1. Field of the Invention
The present invention relates to an imprint apparatus and an imprint method.
2. Related Art
According to dramatic improvement in function of an information or data processing equipment such as a personal computer, an amount of information or data to be handled by a user is significantly increasing. Under such a condition, expectations are raised for an information or data recording/reproducing apparatus with a significantly high recording density and a semiconductor device with a significantly high integration degree as compared with conventional ones.
In order to improve the recording density, a further fine working technique is required. It is possible to perform a fine working on a large area at a time in a conventional lithography technique using an exposure process. However, since such a technique does not have a resolution with wavelength of light or less, it is difficult to produce a fine structure having a size of, for example 200 nm or less. As a technique for forming such a fine structure of 200 nm or less, there are approaches such as an electron beam lithography, a converging ion beam lithography. However, these approaches include such a problem as reduction in throughput.
As a approach for producing a fine structure having a size of wavelength of light or less, there is “NANO-IMPRINT LITHOGRAPHY (NIL) technique” described in U.S. Pat. No. 5,772,905. The nano-imprint lithography technique is a technique for pressing a stamper on which a fine concave and convex pattern is formed in advance by an electron beam lithography or the like on a substrate applied with resist to transfer the concave and convex pattern on a resist layer which is applied on the substrate. A time required for one time processing in the technique can be considerably reduced on, for example, an area of one square inch or more, as compared with the electron beam lithography technique or the converging ion beam lithography.
On the other hand, in recent magnetic recording apparatus, a magnetic disc apparatus, and a hard disc drive apparatus, it is necessary to increase a recording density in a magnetic recording medium in order to meet a demand for increase in a storage volume. However, according to increase in recording density, such a problem is arising that magnetic information recorded by a magnetic recording/reproducing head moving relative to a recording medium influence recording on a track adjacent to the magnetic information. Such a problem can be solved by utilizing a patterning technique separating magnetic materials in adjacent tracks physically (for example, see U.S. Pat. No. 5,723,033).
As the patterning technique for separating magnetic materials on a surface of the magnetic recording medium physically, the above nano-imprint method is effective. When the nano-imprint is used for patterning the magnetic materials on the magnetic recording medium, it is preferable that the imprint is performed at the room temperature and at the atmospheric pressure without performing heating or pressure reducing which requires time for increasing accuracy of pattern transfer at an imprint time and elevating a production efficiency.
Since it is necessary to transfer concave and convex on a resist layer at the room temperature for performing imprint without accompanying heating, it is necessary to make a press pressure higher than that in the imprint process accompanying heating. For example, pressure of at least 100 MPa is required in order to transfer convexconcave on a resist layer of a novolac type commercially available.
On the other hand, a size of a target magnetic recording medium has a doughnut shape with, for example, a diameter of 2.5 inches having a hole with an inner diameter of 20 mm, and a pressure of 30 t is required in order to apply pressure of 100 MPa on a whole face of the magnetic recording medium.
A conventional imprint apparatus is provided with a first press plate having a first press face on which a portion to be pressed including a substrate and an imprint stamper is placed, a pressure applying unit having a shaft and a shaft driving unit for driving the shaft, a second press plate which is connected to a distal end of the shaft and has a second press face opposed to the first press face, where the second press face presses the portion to be pressed placed on the first press face, when the shaft is driven by the shaft driving unit, a first supporting portion on which the first press plate is directly supported and which supports the first press plate, a second supporting portion which supports the pressure applying unit, and a frame structure having a connecting member which connects the first supporting portion and the second supporting portion. As material for the shaft, the first and second plates, and the frame structure, steel or stainless steel which has been subjected to heat treatment is generally used.
The imprint apparatus performs imprint in a state that the portion to be pressed where the imprint stamper and the substrate are opposed to each other is sandwiched between the first press face and the second press face. However, for example, when pressure is applied by a pressure applying unit in the state that the stamper and the substrate are sandwiched between the first press face and the second press face, a pressurizing force of the shaft which presses the portion to be pressed via the second press plate and a reaction force of the frame structure which presses back the portion to be pressed via the first press plate as an reaction to the pressurizing occur. Since acting points of the pressurizing force and the reaction force are different from each other, a structural member between the two acting points deforms.
The pressure acting on the substrate and the stamper becomes uneven within a substrate face due to deformation of the structure and a targeted concave and convex transfer can not be achieved evenly on the whole surface of the substrate, which results in defective transfer.
The defective transfer on the substrate surface occurring due to deformation of the structure causes a pressure concentration on an outer periphery of the substrate and pressure shortage on a central portion thereof.
When an imprint process is performed on a plurality of substrates by a single press working, such a method is effective that the plurality of substrates and stampers are arranged between the first press face and the second press face and a lump imprint is performed. However, pressure unevenness among respective substrates and pressure unevenness within each substrate occur.
The above problem is not exposed in an ordinary die forming work performing work for concave and convex shaping in a micron or millimeter order. However, such a problem has been first exposed in a nano-imprint step for patterning a magnetic recording medium which applies a pressure of 100 MPa or more on the whole face of a disc surface with a diameter of a several centimeters typified by a representative 2.5 inch disc to transfer a fine concave and convex pattern on the face.
As explained above, the nano-imprint approach is a technique which is suitable for producing a fine structure having a size of wavelength of light or less and allows production of a fine structure with a considerably high throughput as compared with a lithographic process performed by the electron beam lithography or the converging ion beam lithography, and it is a technique effective for patterning a magnetic recording medium. However, when a high pressure pressing is performed at the room temperature and at the atmospheric pressure in order to improve a working accuracy and a production efficiency, such a problem occurs that a pattern can not be transferred on a whole face of a medium evenly due to deformation of a pressing machine itself.